Antenna for tire pressure monitoring wheel electronic device

ABSTRACT

An antenna system for a tire pressure monitoring radio frequency (RF) electronic device that includes a printed circuit board (PCB), a ground plane, and an active element. The PCB has a top surface and a bottom surface. The ground plane is on the bottom surface. The active element is mounted on the top surface. The active element includes a first segment positioned in a top surface plane and connected to a second segment oriented at an angle to the top surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.10/322,005, filed Dec. 17, 2002 and entitled “Antenna for Tire PressureMonitoring Wheel Electronic Device,” issued as U.S. Pat. No. 6,933,898on Aug. 23, 2005, which claims the benefit of U.S. provisionalapplication Serial No. 60/360,762 filed Mar. 1, 2002.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a system and method for an antenna fora tire pressure monitoring device having reduced coupling to metalobjects.

2. Background Art

It is known in the automotive industry to provide for wirelessmonitoring of vehicle tire parameters, particularly tire pressure. Insuch tire pressure monitoring systems, tire pressure sensors and radiofrequency (RF) transmitters including antennas are mounted inside eachtire, typically adjacent the inflation valve stem on or near a metalwheel rim. In each tire, the tire pressure sensed by the tire pressuresensor is transmitted as an RF signal by the transmitter through theantenna to a receiver/controller located on the vehicle. The tirepressure information delivered to the receiver/controller by the RFsignals from the transmitters is subsequently conveyed to a vehicleoperator or occupant, typically using a display unit. In such a fashion,tire pressure monitoring systems can help to improve vehicle safety.Exemplary tire pressure monitoring systems are described and shown inU.S. Pat. Nos. 6,112,587 and 6,034,597.

Remote keyless entry (RKE) systems are also well known in the automotiveindustry. RKE systems include an RF transmitter used by the vehicleoperator or occupant to transmit signals that control such functions asdoor, trunk, etc. locking/unlocking, turning on/off lights, sounding analert, arming/disarming an anti-theft system, etc. and areceiver/controller in the vehicle that processes the transmittercontrol signals. The conventional RKE receiver includes an RF antennathat is generally positioned or mounted on or near metal objects such asexterior body sheet metal, internal body structural metal, metal doorskins, etc.

Conventional RF antennas that are mounted near metal objects (e.g., thetire pressure monitoring device antennas that are mounted on the vehiclewheel rims, the RKE antennas that are mounted on body sheet metal, etc.)are de-tuned from one application to the next because of metal couplingbetween active (i.e., radiating or receiving) antenna elements and themetal near the antenna.

Thus, there exits a need for a system and method for an antenna for atire pressure monitoring wheel electronic device and RKE applicationsthat, when mounted on or near metal such as the rim of the wheel or bodysheet metal, reduces or eliminates the metal coupling between theantenna element and the metal. Such an antenna would reduce thede-tuning due to the metal coupling and improve the antenna efficiencyand performance when compared to conventional RF antenna approaches.

SUMMARY OF THE INVENTION

The present invention provides an improved system and method for anantenna assembly that is generally implemented in connection with avehicle tire pressure monitoring wheel transmitter (or similarelectronic device) and mounted on or near the rim of a wheel. Theantenna system of the present invention generally reduces or eliminatesthe coupling between the antenna element and the wheel rim and, thus,reduces de-tuning and improves the antenna efficiency and performancewhen compared to conventional RF antenna approaches. The improvedantenna assembly of the present invention may be advantageouslyimplemented in any system having a radio frequency (RF) transmitter orreceiver antenna that is mounted on or near metal such as a remotekeyless entry (RKE) receiver.

According to the present invention, an antenna system for a radiofrequency (RF) electronic device is provided, the system comprising aprinted circuit board (PCB), a ground plane, and an active element. ThePCB may have a top surface and a bottom surface. The ground plane may beon the bottom surface. The active element may be mounted on the topsurface. The active element comprises a first segment positioned in atop surface plane and connected to a second segment orientedperpendicular to the top surface.

Also according to the present invention, for use in a vehicle tirepressure monitoring electronic device, an antenna system is providedcomprising a printed circuit board (PCB), a ground plane, and an activeelement. The PCB may have a top surface and a bottom surface. The groundplane may be on the bottom surface. The active element may be mounted onthe top surface, wherein the active element comprises a first segmentpositioned in a top surface plane and connected to a second segmentoriented perpendicular to the top surface, and the bottom surface ismounted on or near a wheel rim.

Further, according to the present invention, for use in a vehicle tirepressure monitoring system, a method of reducing coupling between anantenna and a metal object is provided, the method comprising providinga printed circuit board (PCB) having a top surface and a bottom surface,providing a ground plane on the bottom surface, mounting an activeelement on the top surface, wherein the active element comprises a firstsegment positioned in a top surface plane and connected to a secondsegment oriented perpendicular to the top surface, and mounting thebottom surface on or near a wheel rim.

The above features, and other features and advantages of the presentinvention are readily apparent from the following detailed descriptionsthereof when taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a preferred embodiment of the present invention;and

FIG. 2 is a diagram illustrating alternative applications of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

With reference to the Figures, the preferred embodiments of the presentinvention will now be described in detail. As previously noted, it isknown in the automotive industry to provide for wireless monitoring ofvehicle tire parameters, particularly tire pressure. In such tirepressure monitoring systems, tire pressure sensors and radio frequency(RF) transmitters including antennas are mounted inside each tire,typically adjacent the inflation valve stem on or near a metal wheelrim. In each tire, the tire pressure sensed by the tire pressure sensoris transmitted by the transmitter through the antenna to areceiver/controller located on the vehicle. The tire pressureinformation delivered to the receiver/controller by the RF signals fromthe transmitters is subsequently conveyed to a vehicle operator oroccupant, typically using a display unit.

As previously noted, conventional remote keyless entry (RKE) systemsinclude an RF transmitter used by the vehicle operator or occupant totransmit signals that control such functions as door, trunk, etc.locking/unlocking, turning on/off lights, sounding an alert,arming/disarming an anti-theft system, etc. and a receiver/controller inthe vehicle that processes the transmitter control signals. Theconventional RKE receiver includes an RF antenna that is generallypositioned or mounted on or near metal objects such as exterior bodysheet metal, internal body structural metal, metal door skins, etc.

Conventional RF antennas that are mounted near metal objects (e.g., thetire pressure monitoring device antennas that are mounted on the vehiclewheel rims, the RKE antennas that are mounted on body sheet metal, etc.)are de-tuned from one application to the next because of metal couplingbetween active (i.e., radiating) antenna elements and the metal near theantenna.

Generally, the present invention provides an improved system and methodfor the antenna that is mounted on or near the rim of the wheel andimplemented in connection with the vehicle tire pressure monitoringwheel electronic device (i.e., the transmitter) or the antenna that ismounted on or near body sheet metal or structural metal in connectionwith an RKE receiver. The antenna system of the present inventiongenerally reduces or eliminates the coupling between the antenna elementand the metal and, thus, reduces de-tuning and improves the antennaefficiency and performance when compared to conventional antennaapproaches.

Referring to FIG. 1, a diagram illustrating an antenna system 100 inaccordance with a preferred embodiment of the present invention areshown. In one example, the system 100 may be implemented in connectionwith a vehicle tire pressure monitoring wheel electronic device such asa transmitter or a transmitter/receiver (not shown) that is mounted onor near a rim of the wheel (e.g., internal to the respective tire). Inanother example, the system 100 may be implemented in connection with anRKE system antenna that is mounted on or near metal such as body sheetmetal or body structural metal. The system 100 generally comprises anantenna assembly (or apparatus) 102 mounted on or near a metal object104.

In one example (i.e., the tire pressure monitoring system), the object104 is a rim of a wheel that has a respective tire pressure monitored bythe vehicle tire pressure monitoring wheel electronic device. In anotherexample (i.e., a remote keyless entry (RKE) system, not shown), theobject 104 may be any appropriate vehicle metal surface (e.g., bodysheet metal, metal door skin, etc.). However, the system 100 of thepresent invention may be advantageously implemented in connection withany appropriate radio frequency (RF) transmitter or receiver that ismounted on or very near to metal.

The assembly 102 generally comprises a printed circuit board (PCB) 110having an upper surface (or top side) and a lower surface (or bottomside). An antenna element 112 is generally mounted on (or to) the uppersurface of the PCB 110. The lower surface of the PCB 110 generallycomprises a ground plane 114. The ground plane 114 is generally at aground potential (e.g., VSS). In one example, the ground plane 114 onthe bottom surface of the PCB covers the lower surface of the PCB 110.The antenna element 112 generally comprises an active portion of thesystem 100 (i.e., a portion or section of the system 100 that receivesor transmits at least one RF signal).

The element 112 generally comprises a first segment (portion, section,etc.) 120 that may be mounted to the top side of the PCB 110 (i.e.,positioned in the plane of the top surface and substantially parallel tothe ground plane 114) and a second segment (or portion) 122 that may beoriented substantially perpendicular to the top side of the PCB 110. Thesegments 120 and 122 are each generally “C” or “U” shaped. The segments120 and 122 are generally approximately equal in length.

A mounting (or connecting) tab 130 a generally forms an interconnectbetween the segments 120 and 122. The tab 130 a also generally providesa mount for an end of the segment 122 to the PCB 110. A mounting (orconnecting) tab 130 b generally terminates an end of the segment 122that is opposite the tab 130 a and provides another mount for thesegment 122 to the PCB 110. A mounting (or connecting) tab 130 cgenerally terminates an end of the segment 120 that is opposite the tab130 a. The segment 122 generally forms an arch between the tabs 130 aand 130 b. However, the element 112 may be implemented having anyappropriate segment 120 and 122 shapes and configurations in connectionwith the ground plane 114 to meet the design criteria of a particularapplication.

The tab 130 b may be connected to a terminal 132. The terminal 132generally provides a signal input/output connection from the antennaactive element 112 to an electronic device (e.g., transmitter orreceiver) that generates and receives the at least one RF signal that istransmitted (or radiated) and received by the antenna 112. The tab 130 cmay be connected to a first terminal of a capacitance 134. Thecapacitance 134 may have a second terminal that is connected to theground potential VSS. The capacitance 134 generally comprises a tuningcapacitance for the system 100.

The bottom (or lower) surface ground plane 114 is generally mounted(i.e., fixed, positioned, fastened, etc.) to the metal 104. The groundplane 114 and the metal 104 may couple to form an effectively largerground plane and, in connection with the segment 122 which is generallyperpendicular to the ground plane, a more efficient antenna system thanconventional antenna approaches.

Referring to FIG. 2, a diagram illustrating a cross section of a vehiclewheel 200 implemented in connection with the present invention showingalternative mounting positions for the antenna assembly 102. The vehiclewheel 200 may be one of a plurality of wheels where tire parameters,especially tire air pressure, are monitored by a tire pressuremonitoring system. The system 100 is generally implemented with oneassembly 102 per wheel 200 on the vehicle having the tire pressuremonitoring system. The wheel 200 generally has at least one assembly 102(e.g., assemblies 102 a-102 n) mounted inside a tire 140 that is mountedto the rim 104.

In one example, the assembly 102 a may be mounted to a portion of therim 104 that is substantially parallel to the tread surface of the tire140. In another example, the assembly 102 b may be mounted on the rim104 near the tire 140 bead retention flange. In yet another example, theassembly 102 n maybe mounted on the tire 140 near the rim 104 (e.g., ator near the bead). The example mounting positions shown in FIG. 2 areonly illustrative of many positions on or near metal 104 that theantenna assembly 102 may be mounted. The present invention is notintended to be limited to the positions shown. The assembly 102 of thepresent invention generally includes the ground plane 114 on the bottomsurface of PCB 110 that is positioned on or near the rim 104 and,thereby, improves the antenna radiation and reception efficiency insteadof reducing the efficiency as in conventional antenna approaches.

In another example (e.g., an implementation of the system 100 inconnection with an RKE system, not shown), the assembly 102 may bemounted on or near any appropriate metal surface (e.g., door skin, bodysheet metal, body structural metal, etc.) to meet the design criteria ofa particular application.

As is readily apparent from the foregoing description, then, the presentinvention generally provides an improved antenna system (e.g., thesystem 100) that may be especially advantageous when implemented inconnection with a vehicle tire pressure monitoring system or vehicle RKEsystem. However, the antenna assembly 102 may be implemented inconnection with any appropriate transmitter and receiver to meet thedesign criteria of a particular application. In particular, the assembly102 generally improves antenna efficiency and reduces or eliminatesfrequency detuning when mounted on or near metal surfaces when comparedto conventional RF antenna assemblies.

While embodiments of the invention have been illustrated and described,it is not intended that these embodiments illustrate and describe allpossible forms of the invention. Rather, the words used in thespecification are words of description rather than limitation, and it isunderstood that various changes may be made without departing from thespirit and scope of the invention.

1. An antenna system for a tire pressure monitoring radio frequency (RF)electronic device, the antenna system for reducing coupling between anactive element of the antenna system and a metal object, the systemcomprising: a printed circuit board (PCB) having a top surface and abottom surface; a ground plane on the bottom surface, wherein the bottomsurface is mounted on or near a metal object comprising a wheel rim; andan active element mounted on the top surface, the active elementcomprising a first and second segment, the first segment positioned in atop surface plane and connected in series to the second segment, thesecond segment positioned in a plane oriented at an angle to the topsurface, the second segment coupled to the top surface at first andsecond ends of the second segment such that an air gap is formed betweenthe top surface and a section of the second segment between the firstand second ends.
 2. The system of claim 1 wherein the first segment is“C” or “U” shaped.
 3. The system of claim 1 wherein the second segmentis “C” or “U” shaped.
 4. The system of claim 1 wherein the secondsegment comprises an arch.
 5. The system of claim 1 wherein the systemfurther comprises a tuning capacitance connected between the firstsegment and the ground plane.
 6. The system of claim 1 wherein thesystem further comprises an input/output connection at an end of thesecond segment opposite the first segment for connection to theelectronic device.
 7. For use in a vehicle tire pressure monitoringelectronic device to reduce coupling between an active element of theelectronic device and a wheel rim, an antenna system comprising: aprinted circuit board (PCB) having a top surface and a bottom surface; aground plane on the bottom surface, wherein the bottom surface ismounted on or near a wheel rim; and an active element mounted on the topsurface, the active element comprising a first and second segment, thefirst segment positioned in a top surface plane and connected in seriesto the second segment, the second segment positioned in a plane orientedat an angle to the top surface, the second segment coupled to the topsurface via first and second ends of the second segment such that an airgap is formed between the top surface and a section of the secondsegment between the first and second ends.
 8. The system of claim 7wherein the first segment is “C” or “U” shaped.
 9. The system of claim 7wherein the second segment is “C” or “U” shaped.
 10. The system of claim7 wherein the second segment comprises an arch.
 11. The system of claim7 wherein the system further comprises a tuning capacitance connectedbetween the first segment and the ground plane.
 12. The system of claim7 wherein the system further comprises an input/output connection at anend of the second segment opposite the first segment for connection tothe electronic device.
 13. For use in a vehicle tire pressure monitoringsystem, a method of reducing coupling between an antenna and a metalobject, the method comprising: providing a printed circuit board (PCB)having a top surface and a bottom surface; providing a ground plane onthe bottom surface, wherein the bottom surface of the PCB is mounted onor near a metal object comprising a wheel rim; and mounting an activeelement on the top surface, wherein the active element comprises a firstand second segment, the first segment is positioned in a top surfaceplane and is connected in series to the second segment, the secondsegment is positioned in a plane oriented at an angle to the topsurface, and the second segment is coupled to the top surface via firstand second ends of the second segment such that an air gap is formedbetween the top surface and a section of the second segment between thefirst and second ends.
 14. The method of claim 13 wherein at least oneof the first segment and the second segment is “C” or “U” shaped. 15.The method of claim 13 wherein the second segment comprises an arch. 16.The method of claim 13 further comprising providing a tuning capacitanceconnected between the first segment and the ground plane.
 17. The methodof claim 13 further comprising providing an input/output connection atan end of the second segment opposite the first segment.
 18. The systemof claim 1 wherein the angle is an obtuse or an acute angle.
 19. Thesystem of claim 7 wherein the angle is an obtuse or an acute angle. 20.The method of claim 13 wherein the angle is an obtuse or an acute angle.